Classifier



CLASSIFIER Original Filed May 1, 1935 5 Sheets-Sheet 1 "I s w Q m b 9 m 9 INVENTOR I HAROLD BOYD COULTER .IIIHH E Hp Ey v I ATTORNEY.

Jan. 25, 1938. H. B. COULTER CLASSIFIER Original Filed Ma 1, 1935 5 Sheets-Sheet 2 m M R Y mw mm WW? m nmsm mm A u t Jan. 25, 1938. H. B. COYULTER CLASSIFIER Original Filed May 1, 1935 5 Sheets-Sheet 3 m fl INVENTOR BOYD COULTER mm ATTORNEY.

jan zs, 1938. H, B, COULTER 2,106,549

' CLASSIFIER Original Filed May 1, 1935 5 Sheets-Sheet 5 FIG.5

INVENTOR m oouursa BY m mm ATTORNEY.

Patented Jan. 25, 1938 2,106,549

rras ATENT- oi-rice it; Elaroid' Boyd Coulter; Mamaroneck, N. Y., .as-

signer to The Don Company, Inc New York; N. 2., a corporation of Delaware Application-May 1, 1935, Serial no. 19,218

Renewed November 10, 1937' 211- Claims. ((31.209-465) This invention relates to apparatus for the bowl shaped tank-having a-marglnal or boundary separation of settleable solids from liquids and wall extending upwardly from the bottom or hot more particularly teapparatus of the type known tom portion "which as usually made is in the as bowl classifiers. Bowl classifiers are of a form of aninverted cone withacentrally located a type of apparatus which has been on the market discharge opening-providing arestricted, but confor several years and they have been produced in stant open communication or passageway at the considerable numbers by the assignee of the lowermost portion of the bowl" section, namely, present invention, namely, by The Dorr Combetween the bowl section'and the trough section. pany, Inc. The general type of classifier form- The eiliuentlaunder with which the bowl section 30 ing the basis of the invention is shown and deis provided is generally arranged so as to receive scribedin the U. S.Letters Patentl,292,237 granted supernatant liquid from near the upper marginal January 21, 1919 covering an invention of Alfred portion of the bowl. The bowl section also has L. Blomfield. The general type of apparatus isa. movable settled-solids raking and conveying also illustrated in the Slade Eatent 1,916,392 .mechamsmsometimes referred to asmechanical r n ed uly' 4, 1933. I rakes-turnable as a rotatable assemblage about 15 While bowl classifiers were originally designed a vertically extending axis and operable over the for and have decidedly advantageous use in the bottom of the tank. This turnable or rotatable ore dressing fields, nevertheless, the use thereof assemblage is provided for raking and scraping has not been confined to these fields, but has exsettled solids or sediment from the diverse sectended into many other fields wherein it is detions of the tank bottom and forieifecting an im- 6- sired to separate different kinds or types of solids P 11118 or viewing and ultimate transferring .of of hydraulic mixtures containing the difierent the raked solids to the. centrally disposed 'distypes of solids, as for example, containing solids charge opening. TheIrotatable assemblage ishaving difierent specific gravities or different therefore frequently referred to as a rotary rak- 5 settling rates, containing solids having diflerent 1, 8 me s sizes, or containing solids having other peculiarly The trough section has a sloping. bottom from different physical or other basically different charwhich. there upwardly e tends in end Wall 911dacteristics. marginal side walls which merge into-the bowl Bowl classifiers of the type described essentialshaped tank thus combining with the bowl in ly comprise a bowl shaped section and an incompleting a liquid holding structure bflsinclined trough section. One of these sections, as The trough section also hasoperatively positioned for example, the bowl section, provides what is therein an agitating and conve in methflnismi referred to as a primary chamber and the other of also sometimes referred to. as mechanical rakesthese sections, as for example, the trough secpreferably provided by ar cipr at fl n a ;.tion, provides what may be referred to as a secscraping mechanical element mounted and actuondary chamber or compartment. These two ated so as to move in a modified or approximately chambersare in direct communication with each D shape cyclic path in which the straight portion other through a relatively constricted opening; of the D is'lowerniostand parallels the sloping the general level of liquid is substantially the same bottom or inclined deck of the tank and in whichin each, there existing a slight level differential the bight portion of the D is uppermost with the 40 primarily incident to difierent specific gravities result that the forward upward movementpf of the baths in the two chambers. According to the raking element takes place when the raking some proposed modes of operation, it is desirable element is in its lowermost position, thereby efthat the liquid mixtureundergoing treatment be fecting a forward and upward transfer of solids introduced into the bowl section so as .to have a along the sloping bottom or inclined deck of, the

predominating overflow over a peripheral weir trough andso that during the return movement with a downward passage from the bowl section along the bight or curved portion of the D there into.the inclined trough section of heavier or is realized much of the agitative eifect to which larger suspended s0lids.. The supernatant liquid solids in the trough are subjected, particularly with fine solids in suspension overflows through as the rakes or blades of the raking element dig 0 a launder leading fromthe bowl section while downwardly intothe heavier or settled solids emerged larger solids or sands are rakedto dispreparatory to the succeeding forward feeding charge from the trough section. movement thereof.

In bowl classifiers of the type under discussion, The machines of the general type in question the bowl section thereof is provided by a circular have proved exceedingly satisfactory in the fields of endeavor to which they have been applied, but

with the passing of time and with industrial -of higher capacities and larger sizes of appaments of the headroom and progress, particularly in respect to the seeking ratus, there has come an opportunity for exceedingly sturdy and compact machines of unusually high capacity;

Frequently where such machines are to be employed there is limitation as to space, more specifically as to headroom, particularly in plants already in existence. Because of thefacts mentioned, it has become important and advisable to design and develop an improved form of apparatus which would meet the particular and exacting requirements. The design ofthe present invention illustrates a construction which isrelatively compact particularly as to the requirerigid and strong. Whilethepresent design is particularly adapted for use in apparatus of relatively large capacities, it is nevertheless adaptable for employment'in the smaller form of apparatus and as a substitute for the embodi-' ments of construction as illustrated in the older patents heretofore referred to. Due to the improvement in capacity of grinding mills and the trend toward higher circulating loads, classifiers must have correspondingly higher capacities. This leads to larger sizes and changes in design and structural features of a character to commercially meet the increasingly heavier load requirements.

The desired ends above referred to are-realized by a construction embodying the following features, to wit, a construction in which:--

1The structu'reabove the bowl or tank spanning the bowl, and supported by the bowl so as to'be carried thereby, is essentially relatively shallow and comprises (a) what may be referred to as two horizontally and transversely spaced horizontallyand longitudinally extending main beams or girders located at opposite sides of and equally distanced from thevertically extending axis of the bowl shaped tank, or what is substantially the same thing, at opposite sides of the vertically extending axis about which the rotatable raking mechanism turns and (1)) two horizontally extending cross braces or transverse members connected to and rigidly connecting the main longitudinals and located at opposite sides and equally distanced from the vertically extending axis of the bowl shaped tank. The main beams and the cross-connecting members just referred to are preferably, but not necessarily, located equal distances from the vertically extending tank axis, so that there results a boxlike structural section providing a' relatively square opening extending downwardly therethrough. This box-like section has been provided struction is preferably provided by a hollow annular member to which there is connected and from'which there depends a hollow cage-like or drum structure that extends downwardly into and through the opening provided by the boxlike section.

2-The turntable construction and more parit is also relatively,

ticularly the ways thereof horizontal thrust bearing which can be relied upon to prevent any tilting of the parts carried by and from the from or out of the normal vertical operable alignment therefor and in the furtherance of. end just referred to, there is also preferably provided an annular cap constituting restraining means for preventing, if abnormaloperating conditions are experienced, an undue lifting or tilting of any section of the turnable member from its normal operating position on the supporting seat therefor.

3-The main beams or girders, while shallow in themselves, are located close to the top portion of the bowl shaped tank and are supported on the tank by short legs or intermediate members and the cage or drum above referred to is relatively. short or shallow and extends downwardly substantially only that distance which is required for affording a proper connection to a rigid rake-arm structure, sometimes referred to as a rake carrying structure, which is provided for the carrying of raking blades that are dependably supported from the rake arm structure and that extend towards and in the immediate region of the bottom portion of the bowl shaped tank. The depending drum or cage essentially .transmits the entire torque forces required for the turning of the rake arm structure whereby, incident to the turning or driving of the drum, there is effected the -turning of the rakes or scrapers along closed paths over diverse sections annular bearing sections or race-- are sufliciently large to provide a turnable member thereof away of the floor or bottom of the bowl or tank. The

rake carrying structure just referred to is preferably.located above the normal or operative water level of, the tank, which operative level is normally determined by the overflow weirs of the efliuent launder section of the tank. The rake arm carrying structure is provided by two sets of arms connected so as to form a rigid cross construction, in which the arms of each set cdnstitute or provide a rigid assembly comprising in effect a single beam which approaches, but which does not equal the full diameter of the interior of the bowl. The construction is such that an upper portion or member provides a direct connection or tension section between the uppermost portion of the arms and a lower section or member provides a compression section between the lowermost portion or section of the arms whereby the extensions or outer end portions ofeach set of arms are in effect provided by the endportion of a relatively continuous beam extending from one side of the tank to the other. The spider-like arm construction preferably comprises as a tension reinforcing element or member a smaller cross construction providing a reinforcing connection immediately above the central portion of the main cross arm construction referred to. This small upper cross is constructed so that at the upper portions thereof the members which are brought into intersecting relationship are suitably connected.

as by welding or by 'a gusset plate, so as to essentially provide a rigid top chord connection.

The two cross members, namely, the small upper I that an exceedingly rigid rake carrying structure I is obtained. This rake carrying structure is preferably provided by assembled I-beams, but it will be manifest that the assemblage of other structural shapes could be brought into effective ethe smaller cross in construction, relatively connection is efiected in any suitable manner either as by welding or through intermediate con-"- nections provided as by channelmembers con-" nected to the cageon the one hand'and to the rigid rake carrying structure on the other-hand thanit would be ii the armcarryingstructure solely at the center section there;

referred to, whereby there is ized a classifier of large capacity, a classifier rigid simple, a classifier functionally efiective tor the Portion a bladed thereby and; therein.

room requirements can be met.

To attain these objects the invention, as already indicated, proposes to-widen the eil'ective A base of support --i'or theraking rotor, and at the same time to provide for a more-eilective torque" transmission from a rotor rake arms.

To this end the invention provides and embodies in the drive head a torque transmitting drive head into the elementin the nature 01' a hollow member adapt-' ed to rotate about ly indicated, port it from the top,

a vertical axis, such as-the and has fixed to its lower end raking assembly or spider construction. ,The

assembly or spider to the hollow member or cage the intersection may be provided within the drum or cylinder in order to secure a desired degree of rigidity and stability for the rake arms in operation. In this preferred embodiment the rake 1 arms of the spider are located above :the liquid level, so that an improved non-submerged drive head arrangement for thesplder a rising cylindrical portion at itslower end with the drive arms; abullg'eaifixed to cylindrical por bull gear for rotation of the spider self-contained, and 1 a companying drawings in rotor with parts method oiiastening the raking 1 H. The bowl in in this type of ang I I Another advantage coincident with the attainment oi improved'stabilization in the operation of the rotor, lies in the fact that the guiding base for the rotor can be disposed horizontally, thereby reducing head room ,tively to a minimum. Y

. The invention possesses other objects and features of advantage, some of which with the loregoing will be set i'orth in the following description. In the following description and in'the claims, parts'will be identified by specific names for conpossible embodiments,

The novel features considered characteristic iorth with particularity and advantages thereof, will best be understood vlandiment when read in connection with the acwhich 1 is a top view upon a bowl classifier,

Fig. 2 is a part sectional side ew of the bowl classifier shown in Fig. i,

Fig. 3 is an enlarged longitudinal through the her, and improved rotary rahng mechanism therein,

Fig. 4 is a perspective view upon the bowl compartment and improved rotary raking mechanism ther, I

I Fig.5 is a detail perspective broken away lustrate the invention, The ,apparatus herein shown to embody the inve tion is a bowl classifier unit as illustrated in and 2; and which is known to include .asessential portions thereof a primary separating compartment in theway oi. a relatively shallow and preferably circular sedimentation tank or bowl l8, and partly underlying the bowl a section view of the raking tomore clearly llof a substantially longitudinal classifier trough ii having a suitably inclined bottom or deck 20 which is shown to extend from below the central of the bowl and at a suitable slope upmachine'is provided with rotary raking mechanism herein collecti'vely indicated by the numeral it, which mechanismopera'tes to transfer settled solids over the bowibottom through the opening it into the cler compartment ii I sign of this raking mechanism constitutes the essentials of this invention all its details further below.

- In the classifying compartment ll there operates a reciprocating rakemechanism 18 for effectrequirements relabelow. Since the tieitwill be described in bowl compartment of the bowl classisecondary separating compartment in the form ing the stepwise conveyance of heavie'r settled solidsupwardly over the inclined bottom or deck 20 to emer ence. This mechanism plays no direct part in this invention, and it is shown to beas of a standardtype as found in Dorr classifiers and toolevers, and leading from the main crankshaft to encircling the intersection 33 inder, or drum, or hollow portion or hollow torsion the respective rake suspensions or rake hangers and 25.

A cleanout opening 21 is indicated in the lower end of the classifying compartment to have a closure 28. Suitable structures -and 3| support the classifying and the bowl compartment respectively.

In the present embodiment the classifying compartment is shown to be equipped with a twin raking mechanism driven from a common main driving or crankshaft although at staggered phases. This indicates on the face of it a relatively larger capacity as compared with single rake classifiers and consequently also a relatively large bowl diameter-although the latter is not necessarily a function of the capacity of the classifier compartment-bearing on the fact that the larger bowl sizes are particularly benefited by the novel rotor drive head arrangement of this invention.

The apparatus so far described includes component parts basically known from the U. S. Patent 1,916,392. However, inasmuch as the invention now revolves primarily and more specifically around improvements in the design of the rotary raking mechanism previously designated by the collective numeral l8, for the sedimentation compartment or bowl l0, such rotary mechanism will now be described in its details.

Referring particularly to Fig. 3, the rotary portion or rotor of the mechanism includes a spider formed by two pairs of arms 32 suitably connected to constitute a rigid cross structure having a point or portion designated as the intersection 33. Preferably one pair of arms 32 is formed by a throughgoingelement 34, while the other two arms extend at right angles from the central portion of the through-going element to which they are shown to be fixed as by tie plates 35 and clips or other suitable means. The central portion of the rotary spider or cross, or the intersection, is reinforced and stiffened by an overlying smaller cross or .element 31 including the central tieplate 38. To the lower side of the rake arms 32 are fastened raking blades 38a by means of brackets 38!), of I-shapedprofile, such specific blade mounting being known. 1

- Fixedly attached to the upper side of the rake arms'32 of the rotary spider and substantially thereof, isa cylmember 39 constituting a cage dimensioned to rise just high enough to findsuitable annular bearin adapted to receivedriving support above the liquid level l3 in the bowl l0 and having longitudinal ribs 39!). .The lower end of the cylinder 39 has a flange 390 by means of which it is attached to the arms 32 of the spider. The upper end of the cylinder 39 is crowned by a suitable annular member 49 having 'a,toothed portion 43a so as to form a bull gear orworm-wheel impulse for the rotor. The rotary movement of the rotor is determined inasmuch as the gear or member! also constitutes an upper bearing raceby which it is adapted to cooperate with an annular support orrace which latter is represented by an annular stationary member 4|. Anti-friction means or balls 42 are interposed between the bearing'races-or members and 4|.

bracing 530. at

stationary bearing A suitable connection between the worm-wheel 40 and the cylinder 39 is realized as by forming the worm-wheel 40 with a short upright cylindrical portion or rigid collar 43 adapted to fit around the upper end portion of the cylinder 39 and to be fixed thereto as by screw bolts 4 4.

The stationary bearing member 4| is formed substantially in the way of an annular trough in which the peripheral or toothed portion of the gear 40 may be housed. An annular co'ver portion 45 flts onto the trough and is attachable thereto by screw bolts 46. The annular trough 4| and the cover portion 45 therefor constitute in The statipnary housing for the worm gear is supported upon a structure or system 49 which extends across the bowl IO and has suitable end supports 50 fixedly associated with the marginal por tion of the bowl.

The supporting structure 49 consists of a pair of parallel beams or channel irons 5| extending over and across the bowl, and suitably spaced from each other to straddle a center line of the bowl.

Transverse or cross members or ties 52 are provided-. between the two beams and connected therewith as by clips or the like. There are also provided diagonal bracing 53, and transverse the end, of the beams 5|. Thus is formed in the supporting structure 49 a centrally located square shaped frame portion inwhich lodges the cylinder 39 of the rotor, and upon which frame portion may be supported the stationary gear casing described above; through the intermediary of an apertured plate member 54. which fits over the square shaped central frame portion of the supporting structure, and upon which plate member the gear casing can be conveniently anchored by screw bolts .55 located in the corner portions of the plate member.

annular feed arrangement encircles the cylinder 39 of the rotor. It comprises an annular feed chamber 55 having an inlet 51 and outlet openings 59 distributed along the bottom, a layer of concrete or other suitable material being applied to cover the bottom of the feed chamber to protect the same against abrasion from the solids carried by the feed. The annular feedchamber 56 is stationary and attached to and suspended the cylinder 39 by having its inner edge portion intervene between the flange 39a of the cylinder 39 and the rake arms. Tie bolts 50 clamp the cylinder, the panic plate 59 ancl the rake arms 32 together into a rigid unit or rotor. Fastenin connections may cross member 31 and the cylinder "39;

Downwardly from the outer lar baflle plate 59 extends a skirt portion 6| which at its lower end is connected with a second annular baffle plate 52, this baiiie plate being somewhat below the liquid level in the bowl. Still further, a cylindrical baiiie 53 also supported upon the rake arms to rotate therewith, is arranged to surround the first-mentioned annular baffle plate 59. Finally, there is provided along the circumference of the second annular baiile plate 62 .a

also be provided between the edge of the annuridge or weir 83a. which terminates just below but close to the liquid level IS in the bowl. 7

The characteristics of a new drive head arrangement for the rotary raking mechanism are furthermore brought out in the perspective views shown in Figs. 4 and 5.

Fig. 4 illustrates the compactness of the drive head, and the improved manner of mounting and supporting the same relative to the bowl; whereas Fig. 5 shows more precisely and impressively the novelty which lies in the rotor structure itself, that is to say, it shows the novel mannerin which a raking spider or cross is combined and connected with parts of the drive head; in other words, Fig. 5 illustrates the novelty which lies in the fact that by the structural combination of the spider with the cylinder 39 the stability of the rotor is increased inasmuch as the free length of therake arms is relatively shortened as the central portion of the spider comes to lie within the boundary of the cylinder 39. Additional stiflening means may be provided for the spider within the cylinder 39, so as to intrinsically as of great stiflness and stability, without necessitating the use'of external bracing between the arms 32 themselves or between the arms 32 and the cylinder 39, such or similar bracing being unfeasiblein view of interfering structure such as the stationary feed chamber 56 and/or the supporting beams 5i.

Other factors in attaining a high degree of stability for the rotor lie in the relatively wide basis of support provided by the annular hearing; and further in the fact that the location of the rake arms above the liquid level reduces the necessary height of the cylinder 39 to a minimum as compared to its diameter, such minimum height being otherwise controlled by the vertical dimensions as required by the beams or channel irons 5i and by the feed chamber I It is furthermore observed in this novel design that the diameter of the cylinder 39 may be freely chosen as large as reasonably desirable, in view the cylinder in turn may thus be chosen of an adequate diameter.

According to known practice, the outlet opening in the bowl bottom shape located preferably in the center of the bowl; or the opening may be elongated andthereby conlying classifier tank; or there may also be provided adjustable of the opening.

Driving means for the raking rotor may be of some suitable kind, and as indicated in Fig. 1 they gate means for varying the size may comprise a worm and woigm shaft 66 mounttem s 5 form ll In the normal operation which is broadly known, the raking rotor is kept rotating in the bowl III by its driving mechanism at a speed which is adequate to cause the raking blades 38a to advance settled solids at the rate desired, but without undue disturbance of the liquid in the bowl, while in the classifier compartment H the reciprocating rakes 2| of the twin rake arrangement are driven by their respective mechanisms to perform their bodily movements in a closed cyclic path.

Feed, such as for, examples. metallurgical pulp, enters the feed chamber 56 through the feed inlet 51 to be distributed to the various outlet openings 58 through'which diverse streams of pulp leave the feed chamber to be intercepted by the underlying annular baflle plate 59. Here the feed is caused to spread radially into a shallow stream which precipitates over the outer edge of the baflle plate 59 while the cylindrical bafile 63 and the skirt portion 6| form the outer and inner limitations respectively between which the feed is confined in its by which it is directed onto the second annular bailie plate 62 where it spreads further in a radial direction only to be introduced into the liquid body in the bowl itself radially and substantially at the liquid level as it traverses the ridge .or weir 63a. Solids of the heavier typeare now caused 'to settle out upon the bowl bottom as the liquid makes its way from the point of-feed introduction to the peripheral overflow weir it of the bowl. Certain finer solids are carried ofi by the overflowing liquid while the settling portion of the solids is caught by the traveling raking blades and slowly advanced towards the outlet opening hi. With the improved construction of the rotary rake mechanism the rakes or raking blades will have a firmer operating engagement upon the load of settled solids so that quivering of the rotoror rake arms will be elim-- inated or subdued. The sludge is thus gradually moved and allowed to drop through the opening it into the classifying compartment H when. the rakes maintain a zone of agitation in which the solids undergo a kind of scrubbing treatment whereby a certain heavier fraction definitely settles out upon the inclined bottom or deck l2 of the classifier compartment, to be conveyed stepwise upwardly along the deck by the reciprocating movement of the rakes until it reaches a point of emergence and eventually a point of delivery from the classifier as the so-called rakeproduct. At the same time certain fine sizes of solids which may have entered the classifier compartment will have been thrown back into suspension by the agitation and will eventually find their way back through the opening I 4 into the bowl compartment and out through the bowl overflow.

The following material is incorporated as it may aid in a ready appreciation and understanding of certain expressions employed in the claims.

31 providing the upperset of arms may be referred to as an uppe cross structure which is in vertical alignment with and that overlies the large cross structure. The plate 35 which connects the lower portion of the long arms 32- may be viewed as a compression plate rigidly connecting upon the supporting structure or sys-' of the. bowl classifier tank to the other. The plate 38 of the smaller cross structure 31 unites the short arms thereof so that they are relatively rigidly connected, or in other words, so that the smaller cross structure constitutes a rigid, relatively self-contained unit. This tie plate 38 may be viewed as a tension member connecting the upper portions of the arms constituting the small cross structure. The arms of the small cross structure are directly connected to the longer arms of the lower cross structure and the smaller cross structure 31 may be viewed as constituting a tension section that connects the upperportion of the lower long arms 32, to wit, the aligned long arms 32 that extend radially in opposite directions from the center. From one point of view this small upper cross structure constitutes the tying tension member for the arms of the large lower longitudinally extending cross structure. From another point of view the connected upper and lower cross structures result in a strong composite cross structure in which the structural members providing the arms, or outhanging portions thereof, are connected in a manner whereby the rake carrying arms are parts of a stiff or rigid beam structure extending approximately from one side of the tank to the other side of the tank. i

The parallel beams or channels 5| may be viewed and arbitrarily termed as horizontally and main beams or girders that are transversely spaced at equal distances from and at opposite sides of the vertically extending'axis about which the raking assemblage turns, or as otherwise expressed, aboutthe vertically extending. axis or center of the tank or bowl. The transverse tie members 52 may be viewed as horizontally but transversely extending members which arelongitudinally spaced. These cross members 52 are connected to and. serve to connect the main longitudinal members or beams 5|. The cross members 52 are also located at equal distances from the opposite sides.

of the axis just referred to and with the main beams define a box-like section providing a vertically extending opening which is preferably substantially square in horizontal cross section. This opening provides a receiving space into and downwardly through which the or hollow drum member 35' extends. The boxlike section provided by the connected main longitudinal beams and trans'versebeams constitutes or provides a main frame or structural base on which the annular stationary turntable member 4| is fixedly secured. In other words, this boxlike section of the frame construction provides a structural foundation, which through the medium of the annular stationary member ll of that which may be viewed and termed as a turntable construction, is fixedly secured and positioned in respect to the bowl or tank Hi. The annular cap, crown or cover member 40 which comprises and provides the worm wheel teeth 40a may be viewed as the rotatable or turnably supported member of; the turntable construction and itis to be noted that the annular. cover portion 45 is detachably secured to the annular stationary member ll. ,By and because of the cover 45 in the relationship shown, there is provided means functioning to prevent any substantial tilting of the turnable member of the turntable construction from the seating position provided there- 'sembly against tilting operative position therefor.

'relation to the bowl.

rotatable cage tion just referred to, there results the large horizontal type of bearing which can be relied upon for properly supporting the'turnable raking and scraping assembly and for maintaining said asfrom the desired normal What is claimed is':

1.' A two compartment classifier having a lower classifying tank provided 'with' an inclined deck and a solids agitating and conveying mechanism therein for advancing settled solids up along said deck, an upper bowl-shaped sedimentation compartment having; associated therewith a rotatable raking structure provided with rotatable rakearms carrying raking blades and adapted for operation with respect to a load of settled solids in the bowl, means. for operatively supporting the rotatable raking structure, means for feeding to the classifier a liquid solids mixture to be treated therein, an efliuent overfiow discharge, and a discharge for the solids from said tank; characterized in that the rotatable raking structure comprises a self-contained rake arm structure constituting a rigid spider having substantially radial arms rigidly and directly interconnected at the center of the spider, and by and from which arms the'raking blades are supported; and in that the rotatable, structure further comprises a movable annular turntable member, ahollowt torsion member of a suitable width and coaxial with and rigidly interconnecting said turntable member and the self-contained rake arm structure, which hollow torsion member thus overlies the center portion of the spider and thereby defines inner and outer rake arm portions of the spider, the width of said torsion member being such as to establish a ratio of lengths of outer to inner rake arm portions by virtue of which ratio the rotatable raking structure is adapted to assure a desired rigidity and-operating stability with regard to stress re-" action from the operating load; and furthermore in that the means for supporting the rotary raking structure comprise structure complementary to said annular turntable member for sustaining the same in predetermined operative 2. An apparatus as defined in and by claim 1, which is further character'fzed by the fact that the rake arm construction comprises a centrally located relatively short-armed auxiliary spider structure which corresponds to and overlies substantially in verticalalignment the inner or central arm portions of the rake arms.

3. An apparatus as defined in and. by claim 1, which is further characterizedby the fact that the rake armconstruction comprises .a centrally located relatively short-armed auxiliary spider structure as a means, to effect reinforcement and increased total rigidity of therake arm construction, which reinforcing spider corresponds to and overlies substantially in vertical alignment the inner central arm portions of the rake'arms, and that the reinforcing spider structure substantially lodges within the boundaries of the hollow of the torsion member.

4. For use in a classifying apparatus a .selfcontained rake structure comprising a rakearm cross structurejadapted for rotary raking operation in' which the connected rake arms extend substantially in an identicalplane, and are essentially provided by structural shapes; a relatively shortarmed although similar auxiliary cross structure overlyingin vertical alignment member of a the central portions of the rake arm cross for reinforcement and increased rigidity thereof, and having its connected short-arms also essenstructural shapes; scraper blades providing raking elements arranged in series along and from each of said rake arms, a

hollow torsion member coaxial with the rotaryintermediate the inner and the outer ends thereof; and an annular turntable member coaxial with the torsion member and rigidly connected with the free end thereof.

5. For use in a classifying apparatus having positive rotation imparting driving means, a rotatably mountable rigid rake construction comarm cross structure, scraper mounted for rotation in said classifying apparatus.

6. A classifier according to claim 1, in which .the torsion member is a cylinder substantially and approximately as wide as it is high.

7. In a classifier apparatus a relatively shallow and directly interconnected,

suitable width coaxial with the rotary axis of rigidly connected thereto at points upon the rake arms, which lie intermediate the inner and outer ends thereof, and which torsion member is dimensioned as to. its relation of height to width to give the rotatable raking construction per se a desired operating stability and rigidity, a rotatably mountable annular turntable member coaxial with the torsion member and rigidly connected with the free end thereof and rotatable therewith and with the rake arms; an annular stationary turntable member adapted for operatively supporting the rotatable turntable memher and thereby said raking-construction; a shallow frame superstructure traversing the tank and having fixed and rigid relationship thereto, and composed mainly of a pair of main beams straddling the center of rake rotation, and of cross-connections therefor, which frame is adapted and designed in adaptation t and substantially closely surrounding her and for supporting said stationary turntable member' to establishv operative raking relation between the rotatable raking construction and the tank bottom.

- 8. Apparatus according to claim 7, in which the raking arms proper extend above-although near to the liquid level in the tank, and in which the rake arm construction and said torsion memthe torsion member is a cylinder extending from the rake arms upwardly and above the liquid level, the height of which torsion member is approximately equal to or less than its width.

9. A settled solids raking device according to claim 7 in which the raking arms proper extend above although near to the liquid level in the tank, and in which the torsion member is a cylinder extending from the rake arms upwardly and above the liquid level. the height of which torsion member, is approximately equal to its width. I

10. A settled solids raking device according to claim 7, in which the raking arms proper extend the beams and the annular feedwell, and in which the'height of the torsion member is approximately equal to its width. 1

11. In a classifier apparatus having positive rotation imparting driving means, a relatively shallow or bowling a bottom discharge for settled solids, eflluent by rotation of about a vertical axis functions to convey settled solids over the tank bottom to said discharge,

and which assembly comprises a radial rake arm tions of the radial rake arms, and which torsion member furthermore is dimensioned as to height and width to establish a relation of said outer and inner rake arm portions, by virtue of. which there is given said rotary raking construction a desired, operating stability and rigidity; a rotatable annular turntable member coaxial with the torsion member and rigidly connected with the free end thereof and rotatable therewith and with the rake arms, and adapted to receive driving impulse from said rotation imparting driving means; an annular. stationary turntable member adapted for operatively supporting said rotatable ends thereof, which torsion mem-' haped sedimentation tank havturntable member and thereby said rotatable raking construction; a frame structure fixedly supported upon the tank and" surrounding said torsion member and adapted for supporting said stationary turntable member to establish operative raking relation between the rotatable raking construction and the tank bottom, and also adapted to support said driving means; and an annular cover means detachably secured to the stationary turntable member so as to overlie the marginal portion of the rotatable annular turntable member and arranged for serving as a member for restraining tilting movement of the rotatable turntable member away from the operany substantial tilting movement during the normal operation thereof.

HARQLD BOYD COULTER. 

